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Hydrodynamics of laser-driven ablation in planar targets

University of British Columbia

A comprehensive experimental and theoretical study of the hydrodynamics of steady state laser-driven ablation in thin planar targets is given. Experiments were performed using a frequency-tripled Neodymium-glass laser which provided a 2 ns FWHM laser pulse at .355 μm wavelength. This was focussed to an 80 μm spot diameter on thin (6 μm to 50 μm) aluminum targets. Target irradiances up to 2 x 1013 W/cm² were achieved. Firstly, theoretical scaling laws for mass ablation rate and ablation pressure are reviewed. These are compared with experimental results obtained from ion calorimeter and Faraday cup measurements. Secondly, target motion was studied using these diagnostics and the results were interpreted by viewing the target as a compressible fluid (shock compressed) which subsequently rarefies. Target rarefaction was also directly observed through measurements of laser transmission or burnthrough. The compressible fluid approach was used to calculate the hydrodynamic efficiency. This calculation requires as parameters the laser intensity, wavelength and target material. It predicts a hydrodynamic efficiency of only 5 % at 1013 W/cm², .355 μm laser light on aluminum targets, in agreement with our experimental measurements.

Text

2010-04-22

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http://hdl.handle.net/2429/24068

Physics

University of British Columbia

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